1. Field of the Invention
This invention relates to a carburetor with an auxiliary accelerator-pump system, and more particularly to a carburetor having an accelerator-pump system which is equipped to cope with fuel leakage into the carburetor intake passage which is due to an ambient temperature rise.
2. Description of the Prior Art
It is known that operational characteristics of an internal combustion engine under cold weather are improved by providing a vacuum-operated auxiliary diaphragm pump in addition to a mechanical accelerator pump. Such pumps are adapted to supply additional fuel to an engine when accelerating or starting, for instance, in cooperation with the sudden opening of the throttle valve in a carburetor.
With prior art diaphragm pumps of this type, the interior of the pump is partitioned by a spring-loaded diaphragm into a vacuum chamber (a vacuum is introduced therein from an intake passage of the carburetor) and a fuel chamber. The vacuum chamber is communicated by way of a temperature responsive valve, which is adapted to be closed at tempertures above a given level, with a vacuum take-off port in an intake passage, while the fuel chamber is connected by way of a first check valve to a lower portion of a fuel reservoir or a float bowl and by way of a second check valve to a pump jet which opens into the intake passage of the carburetor.
When the ambient temperature is raised and hence fuel pressure in the auxiliary accelerator pump is increased, the fuel present in the fuel chamber or in the passage leading thereto tends to leak through the pump jet into the intake passage, thereby providing too rich a mixture charge and thus impairing the desired operation ability of the engine.